OBJECTIVES: (1) Affinity columns containing bound Lewis rat antibody against rat myelin basic protein (anti-MBP) will be used to capture myelin basic protein-serum factors (MBP-SFs) from the sera of normal neonatal and adult Lewis rats. The MBP-SFs will then be eluted with 3M MgCl2 or with pH3 HCl-NaCl buffer, concentrated, and purified. Inhibition radioimmunoassays will be used to monitor the adsorption, elution, and purification processes. The purpose of this work is to obtain direct evidence for the existence of fragments of MBP in the ciiculation and to check their identity. (2) Fully characterized anti-MBP antibodies will be administered to neonatal rats in order to neutralize relatively high amounts of MBP-SF prior to myelination. On the basis that MBP-SF in the neonatal animal may stimulate myelinogenesis in the same way that Westall's MBP-like growth factor (PNAS 75: 4675, 1978) promotes gliosis, immunological interference may result either in myelin-synthesizing deficient rats or in myelin dysgenesis. (3) Attempts will be made to determine whether MBP-SFs in the neonatal and adult rats represent similar sized fragments or whether those in the adult have undergone further fragmentation.